1. Field of the Invention
The invention relates to a process and an apparatus for sluicing residues produced by gasification of ash-containing, especially solid, fuels such as coal, brown coal, lignite and other carbon-containing substances with oxygen or oxygen-containing compounds such as water and/or carbon dioxide. The reaction of the feedstock is carried out at a pressure of 10 to 200 bar. The gasification residues leave the gasification chamber in liquid or plastic state and are converted, in a water bath connected to the gasification chamber, into a solid granulate which may also be fine grained. The granular residues are periodically discharged from the pressure system of the pressure gasification plant by means of a lock vessel filled with water and arranged beneath the water bath.
2. Discussion of the Prior Art
Processes and apparatuses for sluicing the ash must meet a number of requirements. Apart from the fact that their operation must be possible with an economically justifiable expense, it must be ensured that the sluicing of the residue is effected safely and without polluting the environment. Thus, it is absolutely necessary that escape of production gas from the gasification chamber standing under high pressure into the atmosphere is avoided because of the risk of poisoning and explosion. Additionally, care is to be taken that hazardous gases or gases having an unpleasant odor which, for example, are dissolved in the process liquor under pressure and are liberated on depressurization as well as the waste water discharged with the slag do not enter the environment. Finally, the discharge of the granulated slag from the gasification chamber into the sluicing system should be interrupted only for a short time by the sluicing process to avoid backwash or damming up the slag in the gasification chamber and, consequently, blocking of the outlet.
A process for sluicing residues from a gasification chamber under elevated pressure is described in the German Offenlegungsschrift (DE-OS) No. 24 55 127 and involves substantially the use of a water bath for granulating the ash, a lock vessel and a conveyor. After disruption of the connection between the water bath and the lock vessel, the latter is depressurized via a pressure equalization vessel which is connected with the lock vessel and which previously, while the connection between the water bath and the lock vessel was open, had the same water level and, by means of an inert gas pad had also the same pressure as that in the water bath. While the lock vessel is emptied, inert gas under low pressure is introduced into the pressure equalization vessel and, after having emptied the lock vessel and interrupted the connection between the lock vessel and the conveyor, the lock system is again filled up with water and then brought again to the pressure of the gasification chamber by introducing to the pressure equalization vessel an inert gas which is under a higher pressure than that of the gasification chamber.
It is one disadvantage of this prior art process that the lock vessel must be filled up again with water for each operating cycle. This procedure is relatively time-consuming and requires a complicated pressure equalization system with inert gas. Moreover, gases liberated from the water of the lock vessel on depressurization are not prevented from entering the atmosphere.
It is an object of the invention to avoid the disadvantages described above.